Increasing evidence suggests that intrinsic beta cell defects are responsible for human diabetes mellitus. The observation that both circulating insulin levels and the numbers of beta cells are significantly reduced in diabetes calls attention to the need for delineating the mechanisms which control beta cell neogenesis, and insulin biosynthesis, storage and release. The objectives of this study are: 1) to delineate the factors which regulate beta cell neogenesis; 2) to elucidate the genetic mechanisms which control insulin synthesis; 3) to explore the feasibility of utilizing implantation of beta cells maintained in tissue culture as a means for treating diabetics; and 4) to characterize the structure of the beta cell surface. Tissue culture techniques will be used both for transplantation studies and for examination of beta cells from various species, including rodents and primates for extended periods of time under controlled in vitro conditions. The recent development of a transplantable rat insulinoma with high insulin content will facilitate a number of studies in which limitation of starting material posed a major obstacle. These insulinomas will be employed as a source of beta cells for tissue culture, for isolation of beta cell plasma membranes, and for purification of messenger RNA for insulin. Islet cell morphology and beta cell replication will be examined by light and electron microscopy and by radioautography. Insulin biosynthesis will be studied using labeled amino acid precursors and column chromatography and insulin secretion using the double antibody immunoassay technique. Messenger RNA for insulin will be examined using cell-free translation systems, and purified messenger as a template for synthesis of the insulin gene. The structure of the beta cell surface will be investigated by chemical analysis of plasma membranes and by electron microscopy.